This invention relates to a monoclonal antibody (MAb) directed against a serotype-specific outer membrane protein of Haemophilus influenzae type B, a cell line producing the antibody, the purified outer membrane protein and the use of such an antibody or antigen for serotyping, diagnostic and vaccine purposes.
H. influenzae type b is the most common cause of meningitis in children under one year old. The recent emergence and rapid spread of antibiotic resistant strains, particularly those resistant to ampicillin, are causing special problems in treatment. Chemoprophylaxis with rifampin has given encouraging results by reducing the incidence of nasopharyngeal carriage but such an approach has only limited application. Early treatment is essential to prevent complications. A reliable and rapid test is important for identification of the infectious agent after the antibiotic treatment has begun and when viable bacteria are no longer detectable in body fluids. Several immunoassays using polyclonal antisera have been adopted for bacterial antigen detection. They have all shown either poor specificity and/or sensitivity.
Outer membrane proteins (OMPs) found on the cell surface of many gram-negative bacteria have been used in serotyping and immunoprotection studies. The OMPs of H. influenzae type b have received increasing interest as epidemiological markers and as potential vaccinogens for young children. The identification of a common surface antigen for H. influenzae type b has been hampered by the antigenic variability of the OMPs. The advent of MAbs provides the opportunity to analyse the H. influenzae type b surface components with improved accuracy and reproducibility.
U.S. Pat. No. 4,474,758 (inventor: J. S. C. Kuo; issued: 2 Oct. 1984) is concerned with a combined vaccine having two components: Haemophilus influenzae type B and pertussis outer membrane components.
U.S. Pat. No. 4,455,296 (inventors: E. J. Hansen et al; issued: 19 June 1984) is concerned with hybrid cell lines producing monoclonal antibodies directed against Haemophilus influenzae type b. The most useful monoclonal antibody, 6A2, showed activity against four out of six H. influenzae type b strains tested. Later studies by P. A. Julig and E. J. Hansen, published in Infection and Immunity, 49 (3), 819-827 (1985), indicate that this 6A2 monoclonal antibody is actually directed against a lipopolysaccharide (LPS) associated with the 39K outer membrane protein (OMP) of H. influenzae type b (the interaction of LPS and 39K OMP is highly selective for this protein and does not involve other proteins). The inherent toxicity of native LPS moieties of most gram-negative bacteria precludes the utilization of an intact LPS molecule as a vaccine in infants.
There, therefore, remains a need for a monoclonal antibody which recognizes more, if not all known, strains of H. influenzae type b and, at the same time, does not recognize other organisms or material which may be found in conjunction with H. influenzae type b. There also remains the need for a means for diagnosis of H. influenzae type b infections which is fast, specific and sensitive without giving false positive indications of infection.